Top End Damage!!!

[Hoosierd]

OK experts! Hope someone can explain this one. I am the Dad from this original post: http://www.exriders.com/vbb/showthread.php?s=&threadid=415073

So I buy this quad. Figured I would need to replace the cam chain tensioners, maybe the cam chain etc...

I finally get some time off work to wrench on this thing. Note: it has not been started since purchase do to fear of possibly damaging something internally.

Anywho, tear this thing apart and guess what? The rocker faces are junk, one lobes on the rockers are worn, the head and top are both wallerd out at the far bearing surface....what the heck!

So I complete the tear down and pull the cam out and low-and-behold...a tiny ball bearing??? Floating around in the cylinder head beat the crap out of the castings around the cam. WTH did this little thing come from? Checked a parts fiche and I do not see any bitty ball bearings on there? No manual for this thing though will be getting one now for the reassembly procedures.

Now I have yet another "project"......GGGRRRRRRR!!!!!!!!!!!

Sorry had to vent!!! Anyone? Anyone? Bueller?

[m0t0xk1d]

the ball bearing probably cam from the cam bearings. it probably just fell out. is it the stock cam? if it wasnt stock cam then it could of been a hardweld cam which mean you would have need hard weld rocker and the previous owner didnt get the rocker so the cam tore them up. look around for a head on ebay. ive seen them go as low as $30

[Hoosierd]

Thanks for the reply but, no the cam bearings are complete and fine. All the rollers and skirts intact.

Struck a deal on a complete fresh rebuild. Gonna drop that one in and sell this off I guess. Motor is great except the cylinder head bearing races are garbage now. Needs rocker box casting and rockers and 1 valve stem.

Unbeliveable...just my Luck! :mad:

[BM@Ronayers]

Here is a service manual if you still need it.

http://www.mediafire.com/?wgxoedddmyj

[Hoosierd]

Thank you very much! One quicky question. Do you know if there is much differance in the 2000 model? Probably not much but thought I should ask someone familiar first!

[BM@Ronayers]

I am pretty sure that there has not been a change since the 250X. Nothing major anyways.

[Hoosierd]

Thank you VERY much! That will help a ton! Did not get a manual as part of the deal so I really need this. :):D

[Tommy Warren]

could have been a crank bearing that rode up through the timing chain into the top end.....either way if there is a bearing in the top end 9 out of 10 times there is all kinds of crap in the bottom end:(

[Hoosierd]

Thanks for the reply. That is another one of my concerns! ARG...! LOL!

Wanted to update this thread also. Bout a "Fresh rebuild" 300 off the internet.

98 300ex complete motor -300ex stroker motor.New crank kit bored first over new wisco piston,new clutch.ready to put in 250 or 300ex.has not been run ,just finished putting it together.

Waited a week and finally get it to me....it is a 300ex bottom with a 250 top.........WTF!!! I cannot win!

So, anyone know what I am supposed to do with this "valve bracket" do-hickey on the rocker box?

And will this be way down on power campared to the 300?

[Tommy Warren]

i'm gonna need a pic of what your talkin about. And yes if it is a stock 250 head its gonna be down on power If you take a pic of the intake without the carb on I can tell you if its had any headwork.

[QuadCobbler]

I dont think your gonna see that much differance in power. The 250x motor is basicly the same motor as the 300ex except the 300ex as a slightly longer stroke. The stroke may be about 8.2mm more on the 300ex than the 250x, and they both have a 74mm bore

[Tommy Warren]

how will the decompressor work?

[Hoosierd]

Hey All! Sucker of year ribbon wearer here again. :grr:

Thanks all again for the assistance. Just got off the phone with the seller. He claims it is what the Honda dealer called a "stroker" motor.

300 bottom and 250 top. It has been bored to its first over and a domed piston? Wiesco? The pin sets higher so you get more "volume"? This guy talks in a ton of circles and no idea he really knows. Volume is volume and the cc's don't add up but I do understand you can get more power with less.

Also claims the crank has been freshend up and new bearings, cam chain, etc...

I did note the intake looks cleaned up compared to the 300 head. Quite a bit smoother. Not as polished as my 400 but possibly some did some work.

Any ideas if this is legit and equal of a 300 motor or do I spend the winter searching for another head and rocker box and rebuild the original 300. This thing was supossed to be the "turn-key" toy for my 12 year old. It is now a Frankestein savings killer!

ARG!!!!!
:confused: :confused: :confused: :confused:

[Tommy Warren]

unless he is going to let you tear it down and see if the crank and bearings have actually been freshened up I would just assume that it hasen't seem as there is no way to tell. don't let it affect the price at all. sounds hind of sketchy to me is there a way you can see it in person? do you have pics at least?

[Hoosierd]

Oh I can see it alright...I paid a buddy (who lives within a few hours of this guy) to pick it up for me and bring it over to a party we all met at.

So I have it and already, set it in the quad and fired it last night. There is no return on it so I decided to get it finished up last night. Runs fine I guess. Just pretty pissy about the smoke and mirrors up front. And the chance this thing is way down on hp.

Would you happen to know basic HP numbers for each? Say stockers?

The quad has a jet kit, K&N, and DG pipe when purchased with the original 300 motor.

[QuadCobbler]

The HP of a stock 300ex is about 17.8 and I think the 250x is some where around 12.5 to 14 HP. What you said about there being more voulme is correct. If the pin is moved up on the crank when the piston travels down ward the space between the top of the piston and the bottom of the head will be increased, giving it more volume. This means more CC's The domed piston will give it a higher compresion. If the intake looks like it has been cleaned up but is still some what rough it may have been ported and polished. or at least polished. When the intake is polished is not polished smoth but left some what rough. The rough surface causes a better mixture between the air and fule (intake end only) I belive the exhaust side would be polished smoth for better flow. Regaurding the first over bore, asuming you mean the piston size is now 76mm rather than (74mm stock) the motor will now be about 297CC. I would finish the bike and ride it, maybe find some one else with a 300ex and ride their's to compare.

[Hoosierd]

QuadCobbler, Thank you very much for the info. That is exactly what I was looking for. I have it in the quad and running. Knocking pretty darn hard in the top end if you ask me. Gonna pull it back down and remove the rocker box and take a peek. Looks like I will just ride this on the hopes the guy actually knows what he is doing and rebuild the original 300 motor over the winter.

Thanks again! :D